## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$\approx 0.309$
We are asked to use a calculator to compute the result in radian mode and then round-off the result to three decimal places. We get: $\cos (\dfrac{2 \pi}{5})=0. 30901699437 \approx 0.309$